In a data storage system, data is typically stored in the context of a filesystem. In a filesystem structure, in addition to the data there is metadata which includes organizational information about the filesystem, such as directory structure, file creation and modification information, and the locations where blocks of files are actually stored. In a conventional data storage system, a unitary filesystem is utilized, in which both the data and metadata are stored on a disk or some other block-addressable persistent storage such as flash memory arranged as a solid state disk (SSD).
In some conventional data storage systems, the metadata is stored separately from the data on a separate medium. For example, since the metadata is much smaller than the data and it is accessed more frequently, a faster disk technology may be used to store the metadata. Along these lines, suppose that the data is stored on relatively cheap slowly-rotating magnetic rotating disks. In such a case, the metadata may be stored on a faster disk or on an SSD.